Vacuum tube



J1me 1927' L. E. MITCHELL E AL VACUUM TUBE Filed June 5. 1924 jNSZlE'lVTUR5-' Laazs .E'. MTCHE'LL, ARTHUR n7. WEUTE,

73221.3 ATIDHNEM Patented June 14, 1927.

UNITED STATES PATENT orFI-CE.

LORIS E. MITCHELL AND ARTHUR J. WHITE, 01 EAST GLEVELAND,'OHIO, :AS SIGNORS' '10 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK,

VACUUM TUBE.

Application filed June 5,

()ur invention relates to vacuum electric devices and more particularly to methods and means for introducing vaporizable bombardment or by the high-frequency metal are driven out.

heater. I chemical is to perfect the vacuum by combining with any gases, such as oxygen, which may be present and which are freed from the plate and other metal parts during the heating thereof. The object of our invention is to improve the method of vaporizing the chemical and also to provide suitable means for performing such improved method.

When the plate is heated by the high frequency heater or bombardment, the metal plate is seen to glow first at middle portion thereof, and this glow gradually extends to the ends of the plate. It is during this process that the gases remaining in the When the getter is applied at or near the middle of the plate, as is usual, it is completely volatilized in most cases when the middle portion of the plate reaches a red heat. The result is that the getter is driven ofif the plate and deposits on the interior of the glass bulb which forms part of the tube, and is not in proper position to take care of the gases which come ofl from the ends of the metal plate which are the last portions to be heated. According to our invention, we apply the chemical to an end of the plate. To avoid deposit on the wires, which are grouped closely to-,

get-her at the bottom or stem end, we prefer to locate the getter at the up er end, remote from the stem. vMore speci cally, we pro-' vide a getter plate or support upon' which the getter is mounted, and this support or plate is disposed, preferably, at the upper end of the plate. Our invention will be more fully' understood by reference to the accompanying drawing in which Fig. 1 is an elevation of a vacuum tube; Fig. 2 is anelevation at right angles to that shown in Fig. 1; Fig. 3 is an enlarged perspective of One of the chief purposes of the- }21 united to the upper 1924. Serial No. 717,951.

the plate or anode of the device with the getter support attached thereto; Fig. 4 is an enlarged vertical'section of the said plate or anode; Fig. 5 is a top plan view thereof; Fig. 6 is an elevation otanother form of tube to which our invention is applied; Fig. 7 is a partial perspective of the upper portion of the plate or anode; and Fig. 8 is a partial vertical section on the line 8-8 of Fig. 7.

Referring to the drawing, Figs. 1 and 2 show a vacuum tube comprising a bulb 1O with-a base 11. United to the bulb and extending thereinto is the glass stem 12 into which are sealed the leading-in conductors 13 which are united to the supports '14 carrying the anode plate 15, the filament 16, and the grid 17. The etter support plate 18, which, like the anode plate, may be of nickel or molybdenum, is united, preferably by welding, to the anode plate 15 at the upper end thereof. A quantity of getter 19, for instance magnesium metal, is applied to the upper surface of the getter support plate 18.

The form of vacuumtube shown in Fig. 6 comprises elements corresponding to those of the tube shown in Figs. 1 and 2. The anode plate 20 has a getter support plate end thereof, preferably by welding, and the said getter support plate, in this case, extends over the opening of the said plate as shown more particularly in Figs. 7 and 8. The getter, for instance a strip of magnesium 22, s preferably applied to the under surface of the said getter plate.

The heating of the plate 15 in the case of the tube shown in Figs. 1 and 2, or the plate 20 shown in Fig. 6, which is accomplished by means of a high frequency heater or by bombarding, causes the said plate to become very hot and causes it to glow. The result is that the plate gradually heats up throughout its extent, the ends thereof being the last to heat up. The disposition of the getter, according to our invention, causes the getter material to be volatilized after the anode or plate has been heated up and the gases completely driven out therefrom. In the form shown in Figs. 6, 7 and 8, the getter plate 21 extends over the anode plate orifice. It has been found that particularly good results are obtained by causing the etter, such as magnesium, to be volatilized down upon the elements enclosed by the anode plate.

The getter in this case is applied to the under surface of the support plate.

In addition to the getter which is applied to the supports 18 and 21, it is preferred, especially where the bombarding method is used in heating up the metal parts of the tube to drive out the gas therefrom, to apply a quantity of getter 23 preferably to the outside of the plate. This may he applied in the usual location as shown. It is not inconsistent with our invention to apply as much of the getter as desired to any portion of the metal elements. The object of our invention is to insure that there will be a certain amount of getter located at that portion or portions which are last to heat.

What we claim as new and desire to secure by Letters Patent of the United States, 1s:-

l. The method of perfecting a vacuum in an electric vacuum device comprising a metal element which consists in applying a getter to said element and then heating up said element through a high frequency discharge to drive out gases therefrom in such manner that the portion thereof to which said getter is applied is last to heat.

2. The method of perfecting the vacuum in a vacuum tube comprising an anode plate which consists in applving a getter to one end of said plate and, after said tube has been assembled, heating said anode plate through a high frequency discharge in such manner that said end is the last portion of the anode plate to heat up.

3. In a partially completed vacuum tube comprising an enclosing anode open at its upper end, the combination with said anode of a support in heat conductive relation therewith extending over said upper end, and a quantity of getter on the lower surface of said support.

In witness whereof, We have hereunto set our hands this 2nd day of June, 1924.

LORIS E. MITCHELL.

ARTHUR J. WHITE. 

